A number of chemical, bacteriological, medical or industrial processes require a reliable way for the alternate valving of flexible conduits carrying fluids. Further, in the analysis of body fluids such as blood or urine, it is important to have a valving arrangement which can be accurately controlled so that predictably precise samples can be analyzed. Often such control is performed automatically, at predetermined times, when the apparatus is not closely supervised.
Various types of alternating pinch valves have been developed. For example, in U.S. Pat. No. 3,895,649, a solenoid operated hose clamp for alternatingly restricting flow in a pair of flexible tubes is disclosed. Here the pair of flexible tubes are disposed in the valve between a pair of facing jaws. An arm extending from a coil spring sits between the two flexible tubes. Upon operation of the solenoid, which is coupled to the spring arm one tube or the other is alternatingly compressed allowing fluid flow through the other.
A second design is disclosed in U.S. Pat. No. 4,061,142. This is a relatively complex apparatus employing an electric motor powered valve for alternatingly blocking passage of a fluid through one of a pair of pinched tubes. A rotating clam-shell, shaped cam urges one or the other of a pair of hinged arms against a stop, pinching the flexible tube therebetween.
Still another example of a pinch valve is disclosed in U.S. Pat. No. 4,230,151. This describes a pinch valve for alternatingly closing and opening one of a pair of flexible tubes. It comprises a solenoid and plunger affixed abutment and a spring loaded, yielding abutment. The actuating member pinches one hose against the yielding abutment which normally keeps the other hose pinched, but which is thus relieved by the urging of the actuating member against the yielding abutment.
These various devices, as with others available in the marketplace are manufactured from metallic parts; relatively complex in their construction; and expensive to fabricate.
Further, the designs employing solenoids use a standard design which does not achieve an optimum throw of the actuating arm versus power consumed. Thus the solenoid design must consume relatively high amounts of power and be of a bigger size, especially where tubing wall thickness and diameter are larger.
Also the designs employing solenoids, are arranged such that one or both of the flexible tubes is offset from the axis of the solenoid plunger. This also reduces the efficiency of these prior art designs.
It is therefore a primary object of this invention to provide a new and improved valve of the type referred to above having unrestricted flow which is relatively simple in its construction; uses plastic molded parts; and which is inexpensive to fabricate.
It is another object of this invention to provide a pinch valve design employing a novel solenoid configuration which optimizes the length of stroke versus power consumed to provide a relatively efficient valve having a long stroke with low power consumption.
It is still another object of this invention to provide a valve design where both of the flexible tubes are disposed on the longitudinal axis of the solenoid actuaing arm such that efficient use of the solenoid stroke is obtained.